Field of the Invention
The present invention relates to a microfluidic immunoanalysis device and method thereof, and relates particularly to a magnetic bead-based digital microfluidic immunoanalysis device and method thereof.
Description of Related Art
In recent years, immunoassay has become one of the most commonly used detection methods in laboratories, and may be used for detecting the concentration of target objects in biological fluids. The principle of immunoassay is in fixing a capture antibody on a solid phase carrier and adding a target antigen as a target. At this time, the capture antibody on the solid phase carrier and the target antigen acting as the target make a specific bonding, and then the excess substance not bonded is washed and removed. Next, a detection antibody having labels is added to make a specific bonding with the target antigen acting as the target, and then the excess substance not bonded is washed and removed, and whether the target remains is observed and quantified.
A magnetic bead-based digital microfluidic immunoanalysis chip uses magnetic beads as the aforementioned solid phase carrier, and is operated by arranging with a microfluidic system. The main advantages being the amount of sample liquid and detection time required may be significantly reduced. However, before performing the aforementioned washing process, current magnetic bead-based digital microfluidic immunoanalysis chips typically use a single-direction electrowetting-on-dielectric technique or a dual-direction electrowetting-on-dielectric technique to separate the excess waste-liquid. The single-direction electrowetting-on-dielectric technique refers to applying a voltage at one side of a droplet and using a magnetic force to fix the magnetic beads in the droplet, and then removing the excess waste-liquid from the droplet. However, this technique is unable to fix the magnetic beads to persist in the droplet through a magnetic force, so that parts of the magnetic beads are removed along with the excess waste-liquid. Similarly, the dual-direction electrowetting-on-dielectric technique refers to applying a voltage at two respective sides of a droplet to divide the droplet to two portions, and using a magnetic force to fix the magnetic beads in one of the portions and removing the other portion from the droplet as waste-liquid. However, in this technique, the electrodes used for applying a voltage typically are the same size; therefore the two portions divided from the droplet are similar in size, such that part of the magnetic beads still may be removed along with the excess waste-liquid. In this way, current magnetic bead-based digital microfluidic immunoanalysis chips use large amounts of magnetic beads in order to lower the percentage of leaked magnetic beads to lower the effect that leaked magnetic beads has, however the situation of leaked magnetic beads is still unable to be prevented.
Furthermore, when current magnetic bead-based digital microfluidic immunoanalysis chips perform detection, the magnetic beads are dispersed to perform detection, and therefore have the below deficiencies: under conditions where the same amount of sample is used, more magnetic beads are used making the sample disperse on each magnetic bead, such that the labels are dispersed on each magnetic bead and lowering the detection signal of each magnetic bead. In addition, under conditions where the same number of magnetic beads is used, the method of dispersing magnetic beads in the droplet for performing detection makes the detection signal more dispersed. In particular, low concentration conditions may cause the detection signal to be lower than the detection limits of the measuring apparatus and the detection signal may be unable to be measured.